1. Field of the Invention
The present invention relates to an apparatus for supplying air to a compartment, for example in the interior of a vehicle, such as the passenger compartment of a bus. The apparatus comprises a housing having at least one air-inlet opening which can be closed by a freely swinging flap. The apparatus also comprises at least one blower disposed in the housing, and an air outlet leading into the compartment.
2. Description of the Prior Art
In a known apparatus of this general type, a flap of elastically deformable material is secured to the upper edge of a recirculated air inlet opening. Under its own weight, in the closed position, the flap covers the recirculated air inlet opening. Although the flap can be weighted at the lower free edge thereof, so that the flap does not open under slight air-pressure differences, this arrangement has the disadvantage that the blower has to be of correspondingly more powerful design in order to open the flap and to keep it open. This simultaneously increases the noise level of the ventilating or air supply apparatus, which proves to be unpleasent for the driver and passengers. A flap of this type which swings uncontrollably is not suitable for arrangement in the ram air zone, since at an appropriate pressure difference it allows fresh air to pass and thus creates a draft. This is undesirable, for example when starting up in cold weather, if the blower is associated with a heat exchanger which is connected to the coolant circuit of the internal combustion engine. The same disadvantage is known to arise if a freely swinging flap is provided for closing a by-pass to the blower. In order to prevent the uncontrollable admission of fresh air in such an arrangement, thereby creating a draft, there is known to provide inlet openings for fresh air with large flaps which have to be controlled mechanically, hydraulically, or pneumatically. Servomotors or operating cylinders are required for this purpose, and need appropriate control members. The space requirement of such flaps, and their actuating members, is thus rather large. The structural outlay, dead weight, maintenance and servicing costs, and probability of breakdown are all considerable.
In contrast, an object of the present invention is to provide an apparatus for supplying air to compartments, according to which the creation of drafts is prevented when air pressure differences are encountered while structural expenses are kept as low as possible.